This application is a national stage application of PCT/FR01/01484, filed May 15, 2001, and claims the benefit of priority of French Patent Application No. 00/06137, filed May 15, 2000.
The present invention relates to a sensor for measuring physical parameters of a fluid flow, and in particular a de-iced sensor of air total temperature.
An advantageous application of the invention lies in the field of aviation for measuring the total temperature of the air at the inlet to engines and/or outside aircraft.
Numerous de-iced sensors of air total temperature are already known.
Conventionally, as shown in FIGS. 1 and 2, they comprise an air intake 1 fitted on a streamlined body 2 (having an aircraft wing type profile) in which a duct 3 is provided enabling the fluid to be measured to flow and communicating with the air intakes 1 via an inertial separation zone 4. This zone serves to separate the air into elements of mass that is large compared with that of air (water, frost, sand, . . . ) by centrifuging, these elements being removed from the sensor via an ejection zone 5 opposite to the air intake. In order to avoid phenomena of fluid separation in the inertial separation zone 4, holes 6 are formed through the wall thereof on its side opposite from the ejection zone 5 and in communication with the outside via a chamber 7 which extends transversely across the thickness of the streamlined body 2. The pressure difference that exists between the inside and the outside of the sensor enables the boundary layer to be sucked in through the holes 6.
The assembly comprising the air intake 1, the streamlined body 2, the duct 3, the inertial separation zone 4, and the ejection zone 5 is de-iced electrically by heater resistances positioned in grooves 8 formed in the walls.
An element 9 forming a measurement probe extends inside said duct 3. By way of example, this element 9 can be a platinum wire constituting a thermometer resistance which is thermally insulated from the streamlined body 2.
Measurement error associated with the thermometer resistance protected in a de-iced body conventionally includes heater error (error induced by the de-icing system), recovery error (difference between the measurement and the measured quantity when the heating system is not in operation), self-heating error (induced by the feed to the thermometer resistance), conduction error, radiation error, and response time error. Heating error is, in particular, an error that depends on the shape of the sensor and on the power of the de-icing system.
The various wires forming a thermometer resistance or a heater resistance are connected to a plug connector 10.
Conventionally, as shown in FIG. 2, the air intake 1 is rectangular in section and the same applies, at least in part, to the duct 3 which connects to said air intake.
Also conventionally, the plane 11 supporting the chamber 7 and connecting the streamlined body 2 to the air intake 1 lies parallel to the air flow direction, i.e. perpendicular to the plane supporting the air intake 1.
Sensors of the type shown in FIGS. 1 and 2 need to be capable of operating under particularly severe icing conditions, particularly when they are used in aviation for measuring the total temperature of air.
The object of the invention is to propose a novel sensor structure that makes it possible to withstand icing conditions that are even more severe than can be withstood by presently known sensors, and to do so without increasing the electrical power used for de-icing, so as to avoid falsifying the measurements of the probe-forming element.
The solution proposed by the invention is a sensor for measuring physical parameters of a fluid, as defined in claim 1.
In particular, the proposed sensor advantageously comprises a streamlined body, a duct formed through said streamlined body to enable the fluid to flow, an inertial separation zone, a particle injection zone, a system for sucking in the boundary layer made up of a chamber and holes interconnecting the inside and the outside of the sensor, and an air intake terminating the body at one end thereof and opening out into the duct, the sensor being characterized in that the air intake is of inside section that is rounded, at least in part.
The duct in the streamlined body is advantageously also of rounded section.
The plane supporting the boundary layer suction chamber and connecting the streamlined body to the air intake forms a non-zero angle with the fluid flow direction.